In recent years, interventional treatments, such as percutaneous transluminal angioplasty or stent placement for coronary stenosis, have been widely applied for patients who suffer from ischemic heart disease such as myocardial infarction. Interventional treatments provide shorter post-treated hospital stays to patients because methods of these treatments are less invasive to patients. However, patients must receive observations over a long time after hospital stays because restenosis often occurs.
Meanwhile, coronary artery bypass grafting (hereinafter abbreviated to CABG) has been applied for patients. CABG procedures comprise exposing the heart, and performing the anastomosis of the bypass graft to the distal portion of the coronary stenosis to provide blood flow to distal coronary artery. This method offers many advantages to patients in terms of potential for no restenosis in the postoperative period.
CABG, is applicable to many of patients who have some risk factors to the interventional treatment. Risk factors are, for example, restenosis in the post-treated period of interventional treatments, serious heart failure, occlusions or stenosis in a plurality of coronary arteries, calcification in ascending aorta, chronic diseases in brain, kidney, respiratory system and/or the like, and advancing age of patients. But all of theme risk factors to interventional treatments are also risk factors to CABG with cardiopulmonary bypass. Cardiopulmonary bypass has allowed all surgeons to perform the operation with good patency rate, but deleterious effects of cardiopulmonary bypass to patients who have those risk factors are wall documented. In fact, those patients have been abandoned.
If anesthesia and medial sternotomy are able to be applied to those patients mentioned above, CABG procedures would be performed on the beating heart without cardiopulmonary bypass and cardiac arrest. This less invasive technique is called off pump CABG (hereinafter abbreviated to OPCAB) and becoming increasingly popular in terms of a means for saving such an abandoned patient. The anastomosis of the bypass graft is performed under temporary proximal and/or distal occlusion of target coronary artery to provide a bloodless operative field.
Further, the least invasive technique called minimally invasive direct coronary artery bypass grafting (hereinafter abbreviated to MIDCAB) is applied to patients. The procedures of this technique are performed on the beating heart with left or right anterior small thoracotomy and no medial sternotomy. in the case of CABG with medial sternotomy for obtaining exposure of the coronary artery, patients were obliged to stay in hospital for about one month or more and suffered from postoperative pain. In the case of MIDCAB with anterior small thoracotomy, however, patients would take no pain and have good recovery so that they are able to take a meal on the next day after the operation. Thus, MIDCAB offers many advantages to patients in terms of shorter postoperative hospital stays, cost savings, and superior postoperative appearance resulting from decreasing trauma.
In OPCAB and MIDCAB procedures, it is difficult to perform completely the anastomosis of the bypass graft with good patency rate to the target coronary artery in a short time because the heart is beating. In order to resolve the problem, two types of devices for target area stabilization are developed and are in use. One is a compression type stabilizer, and the other is a suction type tissue stabilizer.
The compression type stabilizer comprises, as described in, for example, JP-A-10-5203, an arm and fork-shaped two legs attached at the front end of the arm. The shape and the number of legs are not restricted thereto. While the arm is fixed to a sternum retractor, the two legs compress the target area and restrict the motion of the myocardium. In fact, cardiac output has decreased as the result of direct ventricular compression with reduced stroke.
The suction type tissue stabilizer, an described in, for example, U.S. Pat. No. 5,727,569, immobilizes the target area by providing a sucker to the surface of the target area, attaching the surface to the sucker, and pulling the sucker with the tissue of the heart. However, internal bleeding has been observed in the tissue of the heart surface after operation as the result of suction of tissue at the vacuum pressure of about -350 mmHg. Since the size of the sucker is large, the operative field becomes too small to perform MIDCAB procedure with anterior small thoracotomy.
In OPCAB procedure, it is necessary to rotate the heart to obtain good exposure of the target coronary artery. In the case of obtaining proper exposure of the left coronary artery by medial sternotomy, it is necessary that the heart is rotated to the patient's right. This rotation the heart is generally conducted by inserting a gauze pad at the posterior surface of the heart. However, it is difficult with this technique to obtain excellent exposure of the target coronary artery because degree of the rotation is not controlled. Furthermore, sudden reduction in blood pressure may occur when the surgeon raise the heart to make a space for inserting the gauze pad.
In OPCAB and MIDCAB procedures, the surgeon has to perform the anastomosis in the time for which the blood flow of the target coronary artery can be stopped. A long time occlusion of the target coronary artery for the anastomosis gives the patient extremely dangerous conditions such an ventricular fibrillation or the like. Therefore, the surgeon tries to perform the anastomosis in a short time. This, however, may make unsuccessful anastomosis to invite occlusion of the bypass graft or coronary artery after the operation.
The stenosis at the point of hemostasis of the coronary artery for the anastomosis has often observed in the postoperative period. In order to interrupt the blood flow of the target coronary artery in the area to be anastomosed, the following technique has been generally used: to place a suture around the coronary artery proximal and/or distal to the site of the anastomosis; pass each end of the suture through the passage of a tube; and slide the tube down while pulling up each end of the suture just to the point of hemostasis. However, Endo at. al. report in The Japanese Journal of Thoracic Surgery, Vol. 51, No. 8, page 704 that the post operative cc:lusiom was observed at the point of hemostasis of the coronary artery because the coronary artery would be damaged by receiving overload force to compress the coronary artery. In fact, the force t o compress the coronary artery is not able to be under control according to this technique.
For such a case, in some proposals a flexible and elastic suture made of polyurethane or porous Tefron was used with the purpose of reducing the force applied to the coronary artery, or a Silastic tape was used for wide contact area with the surface of the coronary artery to compress the coronary artery gently. Nevertheless, as a fact, the stenosis or occlusion in the postoperative period has been often observed yet.
In order to reduce the force applied to the coronary artery, the technique of passing the suture through surrounding tissue of the coronary artery has been proposed. The tissue would play a part of a cushion against the force of compression. However, since a needle was used for passing the suture through the tissue around the coronary artery, the coronary artery itself may be injured with the needle. Further, this technique makes the compression force uncertain to occlude the target coronary artery.
An object of the present invention is to provide a device for safely and reliably carrying out OPCAB and MIDCAB.
Another object of the present invention is to prov,te a device used in OPCAB and MIDCAB procedures, which stabilizes anastomosis area without decrease of cardiac output.
Another object of the present invention is to provide a means used in OPCAB and MIDCAB procedures, for obtaining excellent exposure of a target coronary artery to be anastomosed without decrease of cardiac output.
Another object of the present invention is to provide a means used in OPCAB and MIDCAB procedures, which provides a blood flow to the distal myocardium during the anastomosis of a bypass graft to the target coronary artery.
Another object of the present invention is to provide a means used in OPCAB and MIDCAB, which controls a load force to compress the target coronary artery at a minimum load to stop a blood flow.